Millions in U.S. at Risk from Rising Sea Levels: Report

Sea level rise due to global warming has doubled the annual risk of coastal flooding of historic proportions across widespread areas of the United States, according to a report from the non-profit research group Climate Central.

By 2030, the report says, many locations are likely to see storm surges combining with sea level rise to raise waters at least four feet above the local high-tide line. Nearly 5 million U.S. residents live in 2.6 million homes on land below this level. More than 6 million people live on land below 5 feet; by 2050, the study projects that widespread areas will experience coastal floods exceeding this higher level.

In 285 municipalities, more than half the population lives below the 4-foot mark — with Florida, Louisiana, New Jersey and North Carolina being especially vulnerable, according to the report.

Titled “Surging Seas,” the report analyzes how sea level rise caused by global warming is compounding the risk from storm surges throughout the coastal contiguous U.S.

Headquartered in Princeton, New Jersey, Climate Central is a non-profit research and journalism organization focused on climate and energy.

In 2010, researchers at First American Spatial Solutions (FASS) unveiled a model they said showed the impact of storm surge on property insurance losses caused by hurricanes.

Back in 2007, experts at insurance modeling firm Risk Management Solutions (RMS) along with academics from several universities began studying urban coastal flooding and identified the top 10 cites globally with the most property exposure. Miami and New York made that list.

The creators of “Surging Seas” say their model is the first to generate local and national estimates of the land, housing and population in vulnerable low-lying areas, and associate this information with flood risk timelines. The Surging Seas website includes a searchable, interactive online map that zooms down to neighborhood level, and shows risk zones and statistics for 3,000 coastal towns, cities, counties and states affected up to 10 feet above the high tide line.

Of the 285 municipalities where more than half the population lives below the 4-foot mark, 106 of these places are in Florida, 65 are in Louisiana, and 10 or more are in New York (13), New Jersey (22), Maryland (14), Virginia (10) and North Carolina (22). In 676 towns and cities spread across every coastal state in the lower 48 except Maine and Pennsylvania, more than 10 percent of the population lives below the 4-foot mark, according to the research.

Tidal gauge records show that the sea has already risen 8 inches globally during the last century, and projections point to a steep acceleration.

“Sea level rise is not some distant problem that we can just let our children deal with. The risks are imminent and serious,” said report lead author Dr. Ben Strauss of Climate Central. “Just a small amount of sea level rise, including what we may well see within the next 20 years, can turn yesterday’s manageable flood into tomorrow’s potential disaster. Global warming is already making coastal floods more common and damaging.”

The website also shows how the threat from sea level rise and storm surge is expected to increase over time at 55 tidal gauges around the U.S. and near most major coastal cities. At the majority of these gauges, floods high enough to formerly be called worse than once-a-century events have more than doubled in likelihood, the research says.

Land, housing and population vulnerability estimates are based on 2010 Census data and on land elevations relative to potential water levels, and do not take into account potential protections. However, the reports says, properties behind walls or levees may suffer enhanced damage when defenses are overtopped, or during rainstorms, because the same structures that normally keep waters out can keep floodwaters in once they arrive.

Insurance companies have shown increased interest in a link between climate change and catastrophe losses in the U.S. and around the globe.

Lloyd’s of London has called for a redrawing of the lines of risk mitigation and loss sharing between private insurance and government in the U.S. as a result of the growing financial burden of floods and other natural catastrophes.